A federated database system is a type of database management system (DBMS). In a federated database system, a plurality of data sources may be mapped into a single federated database. This federated database may also be known as a virtual database. The federated database presents the data from a plurality of data sources to a client as though the data is located in a single database.
In a federated database system, a query of a plurality of databases may be received at the federated database system. The federated database system decomposes the query into sub-queries that are distributed to a plurality of separate databases. The result of each sub-query may then be aggregated into a single result set by the federated database system. The single result set may be known as a virtual view. The virtual view may be queried by clients to retrieve data from the federated database system.